Klason lignin, α-cellulose and hemicellulose were isolated from Sugi (Cryptomerica japonica D. Don) sapwood. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) of the sapwood and its components were examined. The initial temperature of thermal decomposition was 258 °C for the sapwood, 342 °C for the Klason lignin, 280 °C for the α-cellulose, and 153 °C for the hemicellulose, respectively. The results of analysis of pyroligneous vinegar liquors prepared from the Klason lignin, the α-cellulose and the hemicellulose indicate that methanol, pyrocatechol and guaiacols are derived from the lignin, cyclotene and maltol from the α-cellulose, furans from the α-cellulose and the hemicellulose, and acetic acid from the three components. The sapwood was carbonized at different temperature and holding time under nitrogen gas, to give carbonization products such as wood-vinegar, wood-tar, and charcoal. The amounts of the wood-vinegar and the wood-tar increased with an increase of the carbonization temperature and the holding time. The capillary gas chromatographic analysis of the wood-vinegars suggests that furans and maltol in the wood-vinegar were produced at 250 °C by the thermal decomposition of the cellulose and the hemicellulose, and pyrocatechol and guaiacols in the vicinity of 300 °C by that of the lignin.